Patent Reference 1 and Patent Reference 2 disclose a polyimide siloxane solution composition, which is prepared by polymerizing/imidizing a tetracarboxylic acid component and a diamine component consisting of (a) a diaminopolysiloxane, (b) a diamine having a polar group and (c) a diamine other than (a) and (b).
The polyimide siloxane solution composition may comprise a curable component such as an epoxy compound and a polyvalent isocyanate compound, in addition to a polyimide siloxane, and may be suitably used for the formation of a cured insulating film for electronic parts; for example, the polyimide siloxane solution composition may be applied to a flexible wiring board by screen printing, and then be cured.
Meanwhile, it is required that a polymer solution composition have a long-term viscosity stability (storage stability) for practical use. A solution composition of a polymer having an inadequate solubility such as a polyimide, a solution composition of a polymer having a polar group, and a solution composition having a high polymer solid content, however, is apt to have problems associated with viscosity stability. A further improvement in viscosity stability has been required for a polyimide siloxane solution composition.